|NO.Z.00116|——————————|BigDataEnd|——|Java&MySQL.XML.V07|——|MySQL.v07|schema约束|介绍编写|

一、Schema约束

### --- 什么是Schema

——>        1. Schema是新的XML文档约束, 比DTD强大很多，是DTD 替代者；
——>        2. Schema本身也是XML文档，但Schema文档的扩展名为xsd，而不是xml。
——>        3. Schema 功能更强大，内置多种简单和复杂的数据类型
——>        4. Schema 支持命名空间 (一个XML中可以引入多个约束文档)

二、Schema约束示例：student.xsd

<?xml version="1.0"?>
<xsd:schema xmlns="http://www.yanqi.com/xml"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            targetNamespace="http://www.yanqi.com/xml"
elementFormDefault="qualified">
    
    <xsd:element name="students" type="studentsType"/>
    <xsd:complexType name="studentsType">
        <xsd:sequence>
             <xsd:element name="student" type="studentType" minOccurs="0"
maxOccurs="unbounded"/>
        </xsd:sequence>
    </xsd:complexType>
    <xsd:complexType name="studentType">
        <xsd:sequence>
            <xsd:element name="name" type="xsd:string"/>
            <xsd:element name="age" type="ageType" />
            <xsd:element name="sex" type="sexType" />
        </xsd:sequence>
        <xsd:attribute name="number" type="numberType" use="required"/>
    </xsd:complexType>
    <xsd:simpleType name="sexType">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="male"/>
            <xsd:enumeration value="female"/>
        </xsd:restriction>
    </xsd:simpleType>
    <xsd:simpleType name="ageType">
        <xsd:restriction base="xsd:integer">
            <xsd:minInclusive value="0"/>
            <xsd:maxInclusive value="200"/>
        </xsd:restriction>
    </xsd:simpleType>
    <xsd:simpleType name="numberType">
        <xsd:restriction base="xsd:string">
            <xsd:pattern value="hehe_\d{4}"/>
        </xsd:restriction>
    </xsd:simpleType>
</xsd:schema>

三、Xml Schema的根元素：

四、xml语句

<?xml version="1.0" encoding="UTF-8" ?>
<xsd:schema xmlns="http://www.yanqi.com/xml"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            targetNamespace="http://www.yanqi.com/xml" elementFormDefault="qualified">

    <xsd:element name="students" type="studentsType"/>
    <xsd:complexType name="studentsType">
        <xsd:sequence>
            <xsd:element name="student" type="studentType" minOccurs="0" maxOccurs="unbounded"/>
        </xsd:sequence>
    </xsd:complexType>
    <xsd:complexType name="studentType">
        <xsd:sequence>
            <xsd:element name="name" type="xsd:string"/>
            <xsd:element name="age" type="ageType" />
            <xsd:element name="sex" type="sexType" />
        </xsd:sequence>
        <xsd:attribute name="number" type="numberType" use="required"/>
    </xsd:complexType>
    <xsd:simpleType name="sexType">
        <xsd:restriction base="xsd:string">
            <xsd:enumeration value="male"/>
            <xsd:enumeration value="female"/>
        </xsd:restriction>
    </xsd:simpleType>
    <xsd:simpleType name="ageType">
        <xsd:restriction base="xsd:integer">
            <xsd:minInclusive value="0"/>
            <xsd:maxInclusive value="200"/>
        </xsd:restriction>
    </xsd:simpleType>
    <xsd:simpleType name="numberType">
        <xsd:restriction base="xsd:string">
            <xsd:pattern value="hehe_\d{4}"/>
        </xsd:restriction>
    </xsd:simpleType>
</xsd:schema>

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Walter Savage Landor:strove with none,for none was worth my strife.Nature I loved and, next to Nature, Art:I warm'd both hands before the fire of life.It sinks, and I am ready to depart

                                                                                                                                                   ——W.S.Landor

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